The other day I was trying out different desktop environments, like Pantheon, Gnome, etc.

But when I was trying to install Pantheon/Elementary Shell, it came up with an error, I ignored it thinking it was nothing important (because it was just about the themes). And a few days before that, I was testing out different themes with the window manager and icons, one of the themes happened to be the Elementary Icon pack. Now whenever I try to install something it tells me to type in "sudo apt-get -f install", and when I type it in, I get some errors. Here is the output of my terminal:

@-PC:~$ sudo apt-get install cinnamon
Reading package lists... Done
Building dependency tree
Reading state information... Done
You might want to run 'apt-get -f install' to correct these:
The following packages have unmet dependencies:
cinnamon : Depends: gir1.2-muffin-3.0 but it is not going to be installed
Depends: libmuffin0 (>= 1.1.2) but it is not going to be installed
Depends: caribou but it is not going to be installed
Depends: mesa-utils but it is not going to be installed
Depends: gkbd-capplet but it is not going to be installed
Recommends: nemo but it is not going to be installed
elementary-artwork : Depends: elementary-theme but it is not going to be installed
E: Unmet dependencies. Try 'apt-get -f install' with no packages (or specify a solution).
@-PC:~$ sudo apt-get -f install
Reading package lists... Done
Building dependency tree
Reading state information... Done
Correcting dependencies... Done
The following extra packages will be installed:
elementary-theme
The following NEW packages will be installed:
elementary-theme
0 upgraded, 1 newly installed, 0 to remove and 41 not upgraded.
2 not fully installed or removed.
Need to get 0 B/57.4 kB of archives.
After this operation, 415 kB of additional disk space will be used.
Do you want to continue [Y/n]? y
(Reading database ... 279974 files and directories currently installed.)
Unpacking elementary-theme (from .../elementary-theme_3.2-0~r601+pkg289~quantal1_all.deb) ...
dpkg: error processing /var/cache/apt/archives/elementary-theme_3.2-0~r601+pkg289~quantal1_all.deb (--unpack):
trying to overwrite '/usr/share/themes/elementary/gtk-3.0/toolbar.css', which is also in package elementary 3.1
Errors were encountered while processing:
/var/cache/apt/archives/elementary-theme_3.2-0~r601+pkg289~quantal1_all.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)"

Please help, I can't do anything that I wanted to do now.
P.S. In the notifications place (in unity the top bar, gnome the notification centre at the bottom of the screen) it has an error saying:

An error occurred. Please run Package Manager from the right-click menu or run apt-get in a terminal to see what is wrong.

The Error message was:

Error: BrokenCount > 0". This usually means that your installed packages must have unmet dependencies."*